Controlling the spectral output of a laser through the use of a wavelength-selective component is well known in the art. Typically, a wavelength-selective component is positioned in optical communication with the optical gain region of the laser so as to select a specific wavelength from the output spectrum of the laser. Once an appropriate wavelength is selected, light of this wavelength is re-directed back into the laser's gain region so as to provide the positive feedback required for lasing action.
One type of wavelength-selective component is a tunable Fabry-Perot filter.
By way of example but not limitation, one such tunable Fabry-Perot filter is disclosed in U.S. Pat. No. 5,739,945, issued Apr. 14, 1998 to Parviz Tayebati for ELECTRICALLY TUNABLE OPTICAL FILTER UTILIZING A DEFORMABLE MULTI-LAYER MIRROR, which document is hereby incorporated herein by reference. By way of further example but not limitation, another such tunable Fabry-Perot filter is disclosed in U.S. patent application Ser. No. 09/059,877, filed Apr. 14, 1998 by Parviz Tayebati for ELECTRICALLY TUNABLE FABRY-PEROT STRUCTURE UTILIZING A DEFORMABLE MULTI-LAYER MIRROR AND METHOD OF MAKING THE SAME, which document is also incorporated herein by reference. By way of still further example but not limitation, another such tunable Fabry-Perot filter is disclosed in U.S. patent application Ser. No. 09/105,399, filed Jun. 26, 1998 by Parviz Tayebati et al. for MICROELECTROMECHANICALLY TUNABLE, CONFOCAL, VERTICAL CAVITY SURFACE EMITTING LASER AND FABRY-PEROT FILTER, which document is also hereby incorporated herein by reference.
Unfortunately, using a tunable Fabry-Perot filter as the wavelength-selective component of a tunable laser can introduce complications. For one thing, while the tunable Fabry-Perot filter can be placed in the laser's optical path so as to only pass light of a selected wavelength therethrough, which selected-wavelength light is subsequently re-directed back into the laser's gain region so as to provide the positive feedback required for lasing action, such tunable Fabry-Perot filters also generally reflect a substantial amount of the "rejected"-wavelength light back into the laser's gain region. This reflected, "rejected"-wavelength light can result in undesirable oscillations occurring within the laser and thereby interfere with optimum lasing.
In order to avoid such reflection problems, tunable Fabry-Perot filters are typically placed at an angle (i.e., at a non-perpendicular angle) to the laser's optical path. While such a configuration can reduce or eliminate the aforementioned reflection problems, it can also lead to other problems such as light loss problems, etc.